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Kai Wang Ph.D. University of Wisconsin-Madison
Professor of Physics and Associate Chair, Department of Physics | Doctoral supervisor
2022-06-09 | 7986
School Of Physics
  • Room 208,Institute of Modern Physics
    • Theoretical Elementary Particle Physics


My research field is theoretical elementary particle physics with emphasis on physics beyond the Standard Model, in particular, Large Hadron Collider physics, Higgs phenomenology, heavy flavor physics, dark matter phenomenology, electroweak symmetry breaking models, neutrino models and supersymmetric models.

A full list of My Publications can be accessed through INSPIRE HEP.

Education and Appointments

  • Professor of Physics, Department of Physics, Zhejiang University, since December, 2014

  • Tenure-track Research Professor at Department of Physics, Zhejiang University,    2011-2014

  • Research Associate at IPMU, University of Tokyo,   2008-2011

  • Ph.D. in Theoretical Physics, University of Wisconsin–Madison,   2008

  • M.S. in Theoretical Physics, Oklahoma State University,   2004

  • B.S. in Physics, Zhejiang University,   2000

Research Talks

(Some talks might contain UTF-8 encoding Chinese Character.)

  • Theoretical Review on Muon Anomalous Magnetic Moment (Physics at the High Intensity Frontier in China)

  • Physics Potential of the future LHeC (SJTU/USTC)

  • Precision Measurement of Higgs and Flavor Physics: A supersymmetric example(For Chinese Higgs Factory) 

  • Connecting Yukawas and flavor physics in MSSM(Talk at LHEP 2013) 
    Rare decays in flavor physics often suffer from Helicity suppress and Loop suppress. Helicity flip is a direct consequence of chiral  U(3) symmetry breaking and electroweak symmetry breaking. The identical feature is also shared by the mass generation of SM fermions. In this review, we use MSSM as an example to illustrate an explicit connection between bottom Yukawa coupling and rare decay process of → . We take a symmetry approach to study the common symmetry breaking in supersymmetric correction to bottom quark mass generation and → . We show that Large Peccei-Quinn symmetry breaking effect and R-symmetry breaking effect required by → sγ inevitably lead to significant reduction of bottom Yukawa  yb. To compromise the reduction in bb, a new decay is also needed to keep the Higgs total width as the SM value. 

  • Light Stop in Precision Top Sample(Lanzhou, 2013)
    The uncertainty of tt production cross section measurement at LHC is at a-few-percent level which still allows the stop pair production with identical visible final states 2ℓ nj+ missing ET . In this paper, we attempt to use the existing measurement of polarization in top quark decay to improve the distinction between stop and top quark states. We apply the ATLAS method of W-polarization measurement in semi-leptonic tt final state to semi-leptonic stop pair samples and study its prediction. We find that the faked top events from stop mostly contribute to the left-handed polarized due to reconstruction and may enhance the FL by few percents. The benchmark point with maximal contribution to top events only changes  FL by 1%. After comparing with the current experiments, we conclude that the current measurement of W-polarization in decay cannot exclude the light stop scenario with stop mass around top quark mass. 

  • Neutrino Mass and Its Implications to physics BSM(BCVSPIN 2013 Lecture)
    Lecture given in BCVSPIN 2013 Summer School in Hangzhou. 

  • A SM Higgs or something else?(Talk at USTC, 2012)
    An Introduction of Higgs phenomenology at Hadron colliders and some thoughts on possible scenarios.

  • Revisit to Top AFB at Tevatron(2012 Updated Version at USTC)
    The improved standard model prediction for total top quark forward backward asymmetry of 8.9% at the Tevatron has significantly reduced the long-term discrepancy between the theory value and the experimental observations. The seemingly “last” over-3 σ anomaly is the CDF measurement of AFB(Mtt 450 GeV) and it is not seen by the D0 collaboration. In this paper, we take the CDF measurement to obtain the best-fit parameter space for various previously proposed models, including axigluon, t-channel neutral current, charged current, and diquark models, then study the predictions of the corresponding parameter space on the direct search or indirect constrain. The particular axigluon model is excluded by the LHC dijet search. The t-channel Z model suffer from the Tevatron same-sign dilepton search bound. The t-channel W model and the diquark model both predict significant increase in the production rate of inclusive tt search at the LHC which is not seen. We conclude none of the models are favored by the direct search bound.
    Video of ChalkTalk at Rutgers, 2011

  • Inverse See-saw in Supersymmetry(Talk at Cornell, 2010)
    To generate fermion mass from radiative corrections requires all the chiral symmetries associated with the fermion masses must be broken. So in order to make the radiative generated mass dominant, one can only tune the vacuum expectation to suppress the tree level mass. In this talk, I have presented two examples of fermion mass generation from radiative corrections in supersymmetric models where supersymmetry plays an important role to stabilize the suppressed tree-level masses without unbroken chiral symmetry. 1) To generate neutrino mass in a modified Wyler-Wolfenstein model from radiative corrections. 2) To generate charged lepton masses and down-type quark masses radiatively from Hu vev in MSSM.

  • Explorations of the Top Quark Forward-Backward Asymmetry at the Tevatron(Talk at Yale and BNL, 2010)
    Motivated by recent measurements of the top quark forward-backward asymmetry at the Tevatron, we study two new physics models that can contribute to a large asymmetry in ttbar production. To generate a large asymmetry while keeping the total production cross section unchanged, the new physics model must interfere with the leading QCD qqbar annihilation into ttbar pair. This requirement implies that the new physics can only be s-channel color octet with V-A coupling or t-channel physics. One example is to introduce a fermion number violating scalar with maximal flavor violation in t- channel. Due to spin correlation, Higgs-like scalar (color singlet or octet) mostly contribute to a negative asymmetry. The second model is a variation of chiral color model. To measure correlation between AFB and Mtt is particularly interesting and may provide much information about the couplings without the direct production.

  • Probing B/L Violations in Extended Scalar Models at the LHC(Talk at BNL 2009)
    To test SM global symmetries U(1) Baryon Number or Lepton Number, there have been many attempts in the last decades, for instance, proton decay, neutron/anti-neutron oscillation or neutrinoless double beta decay. We propose two examples in the extended scalar models to test Baryon Number/Lepton Number violations effects at the coming LHC. The fermion number violation coupling enables scalar to couple to same-sign diquark/dilepton. The new color exotics as color sextet scalars can be produced in pair via QCD gauge interaction. It will decay into same-sign diquark. We will use the four top final state to search for color sextet scalar. It contributes to multijet plus same sign dilepton plus large missing transverse energy but the reconstruction is different from SUSY gluino/KK gluon as the same-sign dilepton comes from the resonance.
    Video of Talk at KITP, UCSB

  • Testing Origin of Neutrino Mass at the LHC(Talk at Berkeley and Fermilab, 2008)
    We propose a unique and clean signal to directly test a neutrino mass generation mechanism, namely the triplet model (type-II seesaw), at the CERN Large Hadron Collider. This is achieved by identifying the flavor structure of the lepton number violating decays of the charged Higgs bosons. The observation of singly charged Higgs will be particularly robust to distinguish the Normal Hierarchy (NH), the Inverted Hierarchy (IH) and the Quasi-Degenerate (QD) spectrum for the light neutrino masses since they are independent of the unknown Majorana phases, which could be probed via the doubly charged Higgs decays.

  • Supersymmetry: A Phenomenology Introduction(Short course at ZJU)
    This three-day series of talks is designed to introduce basic collider phenomenology to graduate students at Zhejiang University. Given its rich phenomenology, we take Supersymmetry as an example. 

  • Gauge Mediated Split Supersymmetry(Talk at UC Riverside, 2005)
    SUSY contribution to Flavor violation/CP violation/Proton Decay all can be suppressed by increasing scalar masses. In Soft SUSY breaking lagrangian, gaugino masses/A-terms can only arise after R-symmetry breaking while scalar masses don’t. In Split SUSY case, one may expect a R-symmetry survive to low scale protect gaugino masses and at the same time, scalars are generated at high scale. However, one alternative realization is to introduce a new gauge symmetry, for instance, U(1) B-L and the messenger field couples to the new gaugino directly. Even though R-symmetry is broken, the Standard Model gauginos can only arise from multiple loops thus a naturally splitting between SM gauginos and scalars will arise.

  • A Symmetry Approach to the MSSM mu-term(Talk at UC Santa Cruz, 2004)
    The U(1) symmetry that forbids mu/B-terms in MSSM carries mixed QCD anomaly (SU(3) x SU(3) x U(1)) thus it can be categorized into Peccei-Quinn (PQ) symmetry. A pseudo-Goldstone boson axion is generated along the PQ symmetry breaking. However, the nuclear/cosmological/astrophysical bounds suggest the PQ symmetry breaking scale is coincidentally the intermediated scale in SUGRA mediated SUSY breaking. Thus the electroweak scale mu can be naturally generated by the PQ symmetry breaking and the same time, invisible QCD axion can provide a solution to strong CP problem.

  • Hidden Symmetries and Their Implications(Talk at Berkeley and UCLA, 2004)
    When the accidental global  U(1) symmetries Baryon number and Lepton number are broken by ’t Hooft instanton within the Standard Model, there will be discrete remnants  Z9 or  Z3 known as baryon parity/lepton parity. The discrete remnants are thus free of anomalies and can be embedded into gauged U(1)s and protected from quantum gravity violation. One of the most serious problem of low energy SUSY is that all Dim-6 operators ffff∕Λ2 can be reduced to Dim-5 operators with one SUSY scalar–gaugino loop as ffff∕Λ∕MSUSY , for instance, the proton decay operator QQQℓ. Consequently, even though SUSY does break Baryon number symmetry, it can enhance the Baryon number violation effects. In this case, the gauged Baryon parity can be employed to avoid such fast proton decay.


Atomic Physics (Under)

Particle Physics (Graduate)


1) Searching for the light Higgsinos at the CERN LHeC. 
By Chengcheng Han, Ruibo Li, Ren-Qi Pan, Kai Wang.
[arXiv:1802.03679 [hep-ph]].

2) Quark jet versus gluon jet: deep neural networks with high-level features. 
By Hui Luo, Ming-xing Luo, Kai Wang, Tao Xu, Guohuai Zhu.
[arXiv:1712.03634 [hep-ph]].

3) Probing anomalous $WW\gamma$ triple gauge bosons coupling at the LHeC. 
By Ruibo Li, Xiao-Min Shen, Kai Wang, Tao Xu, Liangliang Zhang, Guohuai Zhu.
[arXiv:1711.05607 [hep-ph]].
Phys.Rev. D97 (2018) no.7, 075043.

4) Collider Phenomenology of $e^{-}e^{-}\to W^{-}W^{-}$. 
By Kai Wang, Tao Xu, Liangliang Zhang.
[arXiv:1610.02618 [hep-ph]].
Phys.Rev. D95 (2017) no.7, 075021.

5) Squarkonium, diquarkonium, and octetonium at the LHC and their diphoton decays. 
By Ming-xing Luo, Kai Wang, Tao Xu, Liangliang Zhang, Guohuai Zhu.
[arXiv:1512.06670 [hep-ph]].
Phys.Rev. D93 (2016) no.5, 055042.

6) Light Higgsino from $A_t$ Dilemma in Rare $B$-decays. 
By Ming-xing Luo, Kai Wang, Tao Xu, Liangliang Zhang, Guohuai Zhu.
[arXiv:1511.09178 [hep-ph]].

7) Neutrino mass generation and singly charged leptonic exotics in $WW$ events. 
By Hui Luo, Ming-xing Luo, Kai Wang, Tao Xu, Guohuai Zhu.
[arXiv:1407.4912 [hep-ph]].
Phys.Lett. B738 (2014) 160-165.

8) Higgs Precision Measurements and Flavor Physics: A Supersymmetric Example. 
By Kai Wang, Guohuai Zhu.
[arXiv:1312.4010 [hep-ph]].
Chin.Sci.Bull. 59 (2014) 3703-3708.

9) Polarization effects in early SUSY searches at the CERN LHC. 
By Kai Wang, Liucheng Wang, Tao Xu, Liangliang Zhang.
[arXiv:1312.1527 [hep-ph]].
Eur.Phys.J. C75 (2015) no.6, 285.

10) Light Top Squark in Precision Top Quark Sample. 
By Xue-Qian Li, Zong-Guo Si, Kai Wang, Liucheng Wang, Liangliang Zhang, Guohuai Zhu.
[arXiv:1311.6874 [hep-ph]].
Phys.Rev. D89 (2014) no.7, 077703.

11) Flavor dependence of annihilation parameters in QCD factorization. 
By Kai Wang, Guohuai Zhu.
[arXiv:1304.7438 [hep-ph]].
Phys.Rev. D88 (2013) 014043.

12) Comprehensive Constraints on a Spin-3/2 Singlet Particle as a Dark Matter Candidate. 
By Ran Ding, Yi Liao, Ji-Yuan Liu, Kai Wang.
[arXiv:1302.4034 [hep-ph]].
JCAP 1305 (2013) 028.

13) What if bb does not dominate the decay of the Higgs-like boson?. 
By Jiwei Ke, Hui Luo, Ming-xing Luo, Tian-yang Shen, Kai Wang, Liucheng Wang, Guohuai Zhu.
[arXiv:1212.6311 [hep-ph]].

14) Revisit to Non-decoupling MSSM. 
By Jiwei Ke, Hui Luo, Ming-xing Luo, Kai Wang, Liucheng Wang, Guohuai Zhu.
[arXiv:1211.2427 [hep-ph]].
Phys.Lett. B723 (2013) 113-119.

15) Searching SUSY Leptonic Partner at the CERN LHC. 
By Jiwei Ke, Ming-Xing Luo, Lian-You Shan, Kai Wang, Liucheng Wang.
[arXiv:1207.0990 [hep-ph]].
Phys.Lett. B718 (2013) 1334-1341.

16) Can Up FCNC solve the $\Delta A_{CP}$ puzzle?. 
By Kai Wang, Guohuai Zhu.
[arXiv:1111.5196 [hep-ph]].
Phys.Lett. B709 (2012) 362-365.

17) Higgs search and flavor-safe fermion mass generation. 
By Hui Luo, Ming-Xing Luo, Kai Wang.
[arXiv:1110.0085 [hep-ph]].
Phys.Lett. B708 (2012) 133-137.

18) A Revisit to Top Quark Forward-Backward Asymmetry. 
By Jing Shu, Kai Wang, Guohuai Zhu.
[arXiv:1104.0083 [hep-ph]].
Phys.Rev. D85 (2012) 034008.

19) NLSP Gluino Search at the Tevatron and early LHC. 
By M. Adeel Ajaib, Tong Li, Qaisar Shafi, Kai Wang.
[arXiv:1011.5518 [hep-ph]].
JHEP 1101 (2011) 028.

20) Inverse seesaw in supersymmetry. 
By Seong Chan Park, Kai Wang.
[arXiv:1011.3621 [hep-ph]].
Phys.Lett. B701 (2011) 107-110.

21) TeV scale horizontal gauge symmetry and its implications in B-physics. 
By Seong Chan Park, Jing Shu, Kai Wang, Tsutomu T. Yanagida.
[arXiv:1008.4445 [hep-ph]].
Phys.Rev. D82 (2010) 114003.

22) Nearly Degenerate Gauginos and Dark Matter at the LHC. 
By Gian F. Giudice, Tao Han, Kai Wang, Lian-Tao Wang.
[arXiv:1004.4902 [hep-ph]].
Phys.Rev. D81 (2010) 115011.

23) Explorations of the Top Quark Forward-Backward Asymmetry at the Tevatron. 
By Jing Shu, Tim M.P. Tait, Kai Wang.
[arXiv:0911.3237 [hep-ph]].
Phys.Rev. D81 (2010) 034012.

24) Axigluon as Possible Explanation for p anti-p ---> t anti-t Forward-Backward Asymmetry. 
By Paul H. Frampton, Jing Shu, Kai Wang.
[arXiv:0911.2955 [hep-ph]].
Phys.Lett. B683 (2010) 294-297.

25) Invisible Higgs decay with B ---> K nu anti-nu constraint. 
By C.S. Kim, Seong Chan Park, Kai Wang, Guohuai Zhu.
[arXiv:0910.4291 [hep-ph]].
Phys.Rev. D81 (2010) 054004.

26) Neutrino mass from a hidden world and its phenomenological implications. 
By Seong Chan Park, Kai Wang, Tsutomu T. Yanagida.
[arXiv:0909.2937 [hep-ph]].
Phys.Lett. B685 (2010) 309-312.

27) Like-sign Di-lepton Signals in Higgsless Models at the LHC. 
By Tao Han, Hai-Shan Liu, Ming-xing Luo, Kai Wang, Wei Wu.
[arXiv:0908.2186 [hep-ph]].
Phys.Rev. D80 (2009) 095010.

28) Triplet Scalars and Dark Matter at the LHC. 
By Pavel Fileviez Perez, Hiren H. Patel, Michael.J. Ramsey-Musolf, Kai Wang.
[arXiv:0811.3957 [hep-ph]].
Phys.Rev. D79 (2009) 055024.

29) Color Sextet Scalars at the CERN Large Hadron Collider. 
By Chuan-Ren Chen, William Klemm, Vikram Rentala, Kai Wang.
[arXiv:0811.2105 [hep-ph]].
Phys.Rev. D79 (2009) 054002.

30) GeV Majorana Neutrinos in Top-quark Decay at the LHC. 
By Zongguo Si, Kai Wang.
[arXiv:0810.5266 [hep-ph]].
Phys.Rev. D79 (2009) 014034.

31) Neutrino Masses and the CERN LHC: Testing Type II Seesaw. 
By Pavel Fileviez Perez, Tao Han, Gui-yu Huang, Tong Li, Kai Wang.
[arXiv:0805.3536 [hep-ph]].
Phys.Rev. D78 (2008) 015018.

32) Testing origin of neutrino masses at the CERN Large Hadron Collider. 
By Kai Wang.

33) Testing a Neutrino Mass Generation Mechanism at the LHC. 
By Pavel Fileviez Perez, Tao Han, Gui-Yu Huang, Tong Li, Kai Wang.
[arXiv:0803.3450 [hep-ph]].
Phys.Rev. D78 (2008) 071301.

34) Pair production of doubly-charged scalars: Neutrino mass constraints and signals at the LHC. 
By Tao Han, Biswarup Mukhopadhyaya, Zongguo Si, Kai Wang.
[arXiv:0706.0441 [hep-ph]].
Phys.Rev. D76 (2007) 075013.

35) Hidden symmetries and their implications for particle physics. 
By Kai Wang.

36) Stabilizing the axion and a natural solution to the mu problem of supersymmetry. 
By Kai Wang.

37) Gauged baryon parity and nucleon stability. 
By K.S. Babu, Ilia Gogoladze, Kai Wang.
Phys.Lett. B570 (2003) 32-38.

38) Stabilizing the axion by discrete gauge symmetries. 
By K.S. Babu, Ilia Gogoladze, Kai Wang.
Phys.Lett. B560 (2003) 214-222.

39) Natural R parity, $\mu$-term, and fermion mass hierarchy from discrete gauge symmetries. 
By K.S. Babu, Ilia Gogoladze, Kai Wang.
Nucl.Phys. B660 (2003) 322-342.

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